[Bug libstdc++/65473] New: Including <ciso646> does not define __GLIBCXX__

[Bug libstdc++/65473] New: Including <ciso646> does not define __GLIBCXX__

[ldionne.2 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65473

            Bug ID: 65473
           Summary: Including <ciso646> does not define __GLIBCXX__
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ldionne.2 at gmail dot com

Hi,

One would expect that including _any_ header from the standard library defines
the relevant detection macros. For example, I usually include the <ciso646>
header to check for libc++ (per http://goo.gl/eXNYJH). However, libstdc++'s
headers do not always define those detection macros.

Regards,
Louis Dionne

[Bug libstdc++/65473] Including <ciso646> does not define __GLIBCXX__

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65473

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Louis Dionne from comment #0)
> One would expect that including _any_ header from the standard library
> defines the relevant detection macros.

That's not true for most of the <cxxx> headers.

[Bug libstdc++/65473] Including <ciso646> does not define __GLIBCXX__

[ldionne.2 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65473

--- Comment #2 from Louis Dionne <ldionne.2 at gmail dot com> ---
Does the standard specify which headers should define those macros? If not,
then it's a QOI issue that could easily be solved. In all cases, does stdcxx
document which headers must be included in order to get those definitions? I
couldn't find it.

[Bug libstdc++/65473] Including <ciso646> does not define __GLIBCXX__

[ldionne.2 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65473

--- Comment #4 from Louis Dionne <ldionne.2 at gmail dot com> ---
(In reply to Jonathan Wakely from comment #3)
> (In reply to Louis Dionne from comment #2)
> > Does the standard specify which headers should define those macros?
> 
> Of course not, __GLIBCXX__ is not specified by the standard at all.

The standard _could_ have said something like: 

    Detection macros must be defined when including the "<xxxxx>" header
    at the very least.

>From your comment, I understand it doesn't.


> [...]
> 
> But the unhelpful answer is "include anything that includes
> <bits/c++config.h>"

Thanks, I now include <cstddef>. I still think it would be a nice improvement
to include "<whatever your configuration header is>" in <ciso646> and to 
document that, especially since it is super easy to do. Also, <ciso646> seems 
well suited for that job since it is said to be empty by the standard, and so 
this gives us a way to include the least amount of stuff while still getting 
the detection macros.

[Bug libstdc++/65473] Including <ciso646> does not define __GLIBCXX__

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65473

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
But there's no such thing as a detection macro in the standard, so it's not
going to talk about where they belong.

[Bug libstdc++/65473] Including <ciso646> does not define __GLIBCXX__

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65473

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Fri Sep  4 09:16:29 2015
New Revision: 227484

URL: https://gcc.gnu.org/viewcvs?rev=227484&root=gcc&view=rev
Log:
Make all <cxxx> headers include <bits/c++config.h>

        PR libstdc++/65473
        * include/c/cassert: Include <bits/c++config.h>.
        * include/c/cerrno: Likewise.
        * include/c/cfloat: Likewise.
        * include/c/ciso646: Likewise.
        * include/c/climits: Likewise.
        * include/c_global/cassert: Likewise.
        * include/c_global/cerrno: Likewise.
        * include/c_global/cfloat: Likewise.
        * include/c_global/ciso646: Likewise.
        * include/c_global/climits: Likewise.
        * include/c_std/cassert: Likewise.
        * include/c_std/cerrno: Likewise.
        * include/c_std/cfloat: Likewise.
        * include/c_std/ciso646: Likewise.
        * include/c_std/climits: Likewise.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/c/cassert
    trunk/libstdc++-v3/include/c/cerrno
    trunk/libstdc++-v3/include/c/cfloat
    trunk/libstdc++-v3/include/c/ciso646
    trunk/libstdc++-v3/include/c/climits
    trunk/libstdc++-v3/include/c_global/cassert
    trunk/libstdc++-v3/include/c_global/cerrno
    trunk/libstdc++-v3/include/c_global/cfloat
    trunk/libstdc++-v3/include/c_global/ciso646
    trunk/libstdc++-v3/include/c_global/climits
    trunk/libstdc++-v3/include/c_std/cassert
    trunk/libstdc++-v3/include/c_std/cerrno
    trunk/libstdc++-v3/include/c_std/cfloat
    trunk/libstdc++-v3/include/c_std/ciso646
    trunk/libstdc++-v3/include/c_std/climits

[Bug libstdc++/65473] Including <ciso646> does not define __GLIBCXX__

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65473

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |6.0

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
All libstdc++ headers should include c++config.h now.